The present invention relates to a liner for a substantially undeformable teatcup shell for forming a two-chambered teatcup, by means of which milk is extracted from a teat in a suction milking process through a milking vacuum during a milking phase and the teat is massaged during a rest phase.
In a milking machine the liner (or teatcup liner or teat rubber) forms the contact zone between the milking machine and the animal to be milked and, therefore, constitutes a part of the milking machine which is essential, but not easy to design. It is particularly difficult to design the head part together with the head hole opening of the liner (teat liner) which have to achieve several functions: the head hole opening or, in other words, the insertion opening for the teat has to adapt itself well to the different teat shapes and sizes as well as teat positions and conditions in order to seal the milking vacuum being present under the teats against environment pressure. Hereby, however, the teats must not be constricted since pains and swellings occurr in the teat skin in case of restriction of the blood circulation. If these occur, due to tenseness of the udder musculature the degree of emptying the udder decreases, the milking time increases and the strippings (milk which has to be milked from the udder by particular milking labor after xe2x80x9cnormal milkingxe2x80x9d) increases.
In the region of the Fuerstenberg Vein Ring at the transition region from the teats to the udder bottom there are particularly many blood and lymph vessels. Since this region, being an infection barrier, already in the natural state constitutes a bottleneck, there is a danger of obstruction of the milk discharge in case of constrictions of the blood and lymph vessels due to hard liners having narrow insertion openings, which results in closing of the bottleneck by swelling. In order to pass this swollen bottleneck and to obtain the remaining milk, the teatcup cluster or the single teatcups have to be drawn downwards away from the udder. This operation, called xe2x80x9cstrippingxe2x80x9d, requires additional man power or sophisticated apparatuses and prolongs the milking operation considerably. The stress on the teat tissue during this time period is particularly high because only little milk flows and accordingly the highest milking vacuum acts on the teats. Teat damages with subsequent problems of udder health may result from this.
Furthermore, an essential quality criterion for liners consists in how well the liners hold the teatcups in an optimum milking position still below the Fuerstenberg Vein Ring although a continued suction acts on the teats by means of the applied milking vacuum.
In known liners for two-chambered teatcup assemblies for a suction milking process, a head part is contiguous to the end of the tube part facing the udder because of the following reason. The tube part, called xe2x80x9cshaft partxe2x80x9d or xe2x80x9cbarrel partxe2x80x9d (hereinafter xe2x80x9cbarrel partxe2x80x9d), is inserted in a rigid or undeformable teatcup (milking cup) coaxially to the latter such that between the barrel and the teatcup a closed annular space is formed which is in communication with a pulsator. Depending on the milking principle used, by means of the pulsator, this space is alternatingly supplied with vacuum in the milking (or suction or suctioning) phase (hereinafter xe2x80x9cmilking phasexe2x80x9d) and is supplied with air under atmospheric pressure or overpressure in the relief or rest phase (hereinafter xe2x80x9crest phasexe2x80x9d). In any case between the inner part of the barrel, in which during milking the teat is disposed, and the annular space there is a pressure difference by means of which the tube part is folded. The pressure on the teat resulting therefrom massages back from the teat tip the blood and the tissue liquid suctioned by the milking vacuum together with the milk. In order to stretch the closing muscle of the teats in the milking phase the space under vacuum must have a cross section which ist slightly larger than the teat. Therefore, the tube part, which is continuously folding and partly also over-stretched by the higher vacuum in the annular space, rests only insufficiently tightly on the teat and allows only a very poor adhesion on the teat. This is the reason why, at the side of the liner shaft facing the udder, an additional sealing element, which is typically referred to as xe2x80x9cliner headxe2x80x9d, is required.
Examples of liner heads are known wherein the insertion openings for the teats are shaped as annular lips. In DE 196 23 386 A1 an example is described wherein the annular lip is provided with an additional tube part in order to increase the bearing area on the teats and, hence, to reduce the bearing pressure. This tube part, however, is variable only to a small degree in its diameter.
Other examples are described inter alia in DE 29 41 150 C2 and DE 196 35 719 A1. In cases where these liners with the relatively small sealing lip are produced of hard material, they seal well, but they press in a deforming manner in particular into thick teats, thereby constricting them and restricting the area of the Fuerstenberg Vein Ring at the transition from the teat to the udder bottom. In many cases they are not satisfactory with respect to their physiological properties, and have only limited adaptability to different teat sizes. In cases where these liners have soft and flexible annular lips, they can adapt well to the teats, but there is a tendency for air intrusions to occur. Therefore, they adhere worse and soon start to climb up or to slip down the teat. Furthermore, particularly, soft liner heads having thin walls are subject to high wear.
The drawings of DE 38 10 160 A1 and of DE 198 12 573 A1 show liners, the head part of which is each shaped as a continuation of the tube part without transition. In both examples there is no sealing annular lip, but no closed annular space independent from the pulse space is described which would be able to adapt itself to different and, in particular, to small teat sizes.
Namely, nothing can be learned from any of the previously mentioned documents about the design of the shown head part, least of all with respect to the functioning thereof or the importance for the tightness of the teat rubber: DE 38 10 160 A1 is directed to compensate for cyclic fluctuations of the negative pressure in the teatcup cluster by means of a control valve operated in a particular manner. The illustration of the head part is such that the upper end of the barrel part is turned up toward the outside and is attached to the outside of the barrel part below or is only resting closely on it. The turned-up part rests at the transition area from the teat to the udder and is located further radially outside with respect to the barrel part. On the other hand, DE 198 12 573 A1 seeks to provide a teatcup cluster which functions without a pulsator. This is achieved by providing a direct connection pipe between one of the pulse spaces of the teatcup cluster and a negative-pressure area of the teatcup cluster, as well as a switching valve positioned in the connection pipe, the switching valve in its suction position unblocking the connection pipe and in its relief or rest position throttling the connection pipe, wherein in the rest position the pulse space is connected with a pressure gas source. The head part is also illustrated as being a turn-up of the upper end of the barrel part toward the outside attached below at the outside of the barrel part. The inner width thereof is larger than the largest inner width of the barrel part.
In the document U.S. Pat. No. 4,249,481 a liner having an upper end shaped as an annular tube is described. The teat-surrounding tube part of the described liner has a double wall, the thus formed annular chamber, at the udder-side end, ending in an annular space, which is somewhat enlarged radially toward the outside, and which is provided with a connection part for being alternatingly supplied with pressure and vacuum. This liner is provided for pressing out the milk from the teat. Since, according to the description, the annular space has to be vacuum-resistant, it cannot be manufactured in a very large and soft shape, which adversely affects a good adaptability to the teat.
EP 266 809 B1 discloses a liner used in a pressure milking process in which the milking with hands serves as a model. The sealing lip here has a prolongation which is turned up toward the inside and toward the bottom. The lower end of the prolongation is pressed at the upper end of a tube part by means of a rigid ring in order to form a tight connection with this tube part, which from the hygienic point of view may be problematic. Thereby an annular space surrounding the teat is formed which is in connection with the space between teatcup shell (teatcup sleeve or simply shell) and tube part. In different milking phases these spaces are alternatingly supplied with pressured air and vacuum. Thereby the prolongation in one phase presses onto the teat and thus squeezes the milk out of the teat, and in the other phase stretches the teat for allowing milk to flow again into the teat. Hence, this annular spacexe2x80x94facing the udderxe2x80x94has a milking function. The function of sealing towards the teat, therefore, is taken over by that upper part of the annular space which is formed in a stronger way and is resting on the teat, i.e. the sealing lip. With such a pressure milking process a sufficient milking speed cannot be achieved. Furthermore, on a long-term the teats are damaged.
The object of the present invention is to provide a long wearing liner for a two-chambered teatcup for a suction milking process which adheres very well even with strongly different teat sizes and with low milking vacuum, which does not cause air intrusions and does not climb up even with low weight of the teatcup cluster, but which does not constrict the teats, and thus allows the milking of nearly the entire milk which is available, without additional stripping labor being required.
This object is achieved with a liner according to claim 1. Advantageous embodiments of the invention are the subject-matter of the subclaims.
When the inventive liner is pushed onto a teat which is much thicker than the inner width of the annular tube, the elastic annular tube is widened by the teat and is lengthened in the axial direction thereof. Due to such widening and axial lengthening, the surface area of the annular tube bearing on the teat is increased, which on the one hand increases the sealing effect and on the other hand keeps the pressure on the teat small. In a case where the inventive liner is pushed onto a teat which is only slightly thicker than the inner width of the annular tube, the milking vacuum which is supplied permanently in the barrel part results in the annular tube being drawn radially toward the inside and toward the bottom and the annular tube resting in a sealing manner on the teat. In this case, too, a large and thus gentle bearing surface of the liner on the teat is achieved. The effect of the milking vacuum of course also occurs with thick teats. With teats oriented in an oblique manner or being irregularly shaped, the annular tube may deform also in a non-rotationally-symmetric manner, and thus may softly and sealingly adapt to the given physiological geometry. Therefore, the inventive liner adapts to the different teat shapes without any problem. Furthermore, by automatic reduction of the inner width of the teat rubber, it compensates for the teat becoming flabbier and flabbier in the course of the milking, and thus avoids air intrusions. In other words, the annular tube always serves for sealing and never for milking as such. Additionally, by designing the sealing part of the inventive liner as an annular tube, a frequent widening and over-stretching and resulting permanent deformation of the head partxe2x80x94as is the case with a sealing lipxe2x80x94is avoided, which results in longer running times, and thus improved economic efficiency.